1. Field of Invention
The present invention relates to electro-optical devices and electronic apparatuses, and more specifically, it relates to an electro-optical device to drive a current-driven element and to an electronic apparatus.
2. Description of Related Art
In the related art, various electro-optical devices such as organic EL panels with current-driven elements have been disclosed. As illustrated in FIG. 18, a related art electro-optical device includes a matrix display portion 100 with a plurality of current-drive elements (not shown), a frame portion 101 formed at the periphery of the matrix display portion 100, a mounting terminal portion 102 provided at one edge of the frame portion 101, a power source bus line 103, which is a conductive line arranged in the frame portion 101 and which is connected to the mounting terminal portion 102, and n (n≧1) power source lines 104 connected to the power source bus line 103, the power source lines 104 supplying driving current to the current-drive elements.
The frame portion 101 includes a first region 101a, which is formed at the periphery of the matrix display portion 100, including the mounting terminal portion 102, a second region 101b arranged so that the matrix display portion 100 is interposed between the first region 101a and the second region 101b, and a third region 101c and a fourth region 101d to connect the second region 101b to the first region 101a.
The power source bus line 103 includes one continuous conductive line and is made of a metal such as Al or AlSiCu. The power source bus line 103 includes a power source supply portion 103b provided in the part of the frame portion 101 on one side (the second region 101b in this related art) and connected to the plurality of power source lines 104, and a conductive portion 103a (that is arranged in the third region 101c in this related art) to connect one end of the power source supply portion 103b to the mounting terminal portion 102. The conductive portion 103a has a section whose width is W1 and whose height (thickness) is t. The supply portion 103b has a section whose width is W2 and whose height (thickness) is t. The n power source lines 104 are all led out from the supply portion 103b and are connected to the current-drive element.
The driving current of the current-drive element is supplied from the mounting terminal portion 102 to the device, passes through the conductive portion 103a of the power source bus line 103, is led to the supply portion 103b, is sent into the respective power source lines 104, and is supplied to each current-drive element.
However, the aforementioned related art technology has the following problems.
First, as illustrated in FIG. 18, in order to arrange the conductive portion 103a in the third region 101c, the third region 101c of the frame portion 101 becomes wider by the width W1 of the conductive portion 103a. It is preferable that the frame portion 101 formed at the periphery of the matrix display portion 100 be as narrow as possible for purposes of miniaturization.
Second, as illustrated in FIG. 18, in the case where the position of the connection between the mounting terminal portion 102 and the conductive portion 103a, that is, the feeding point of the corresponding electro-optical device is made point A, the position where the power source line 104 X1 closest to the conductive portion 103a is connected to the supply portion 103b is made point B, and the position where the power source line 104 Xn remotest from the conductive portion 103a is connected to the supply portion 103b is made point C, electric potentials in the respective points A, B, and C are indicated as VA, VB, and VC, voltage drops by V1 at the point C separated from the point B by the distance L1, as illustrated in FIG. 19. For simplification, the graph of FIG. 19 illustrates a construction wherein almost constant current is supplied to all of the current-drive elements.
Because the current supplied to each current-drive element varies according to applied voltage, the voltage drop causes unevenness in current supply in the direction parallel to the supply portion 103b (in general, the direction parallel to the signal line (a scanning line (not shown)) by which the timing of supply of the data of each current-drive element is controlled). In the case where the current-drive element is a light emitting element, the voltage drop causes brightness unevenness. Thus, the display quality of the electro-optical device deteriorates. Even if the influence of static voltage error is excluded using a current program circuit, the common impedance of the supply portion 103b is large. Thus, unevenness in dynamic current supply and brightness unevenness is caused by the dynamic voltage variation, and deterioration in the display quality results.
Furthermore, as illustrated in FIG. 18, when a position closest to the power source line 104X1 is the point D and when VD indicates voltage value at the point D, as illustrated in FIG. 20, there is the problem that voltage value VD is reduced by the electric potential difference V2 from VB at the point B separated from the point D by the distance L2.
This voltage drop causes brightness unevenness in a vertical direction, and thereby deteriorates the display quality of the electro-optical device. Even if the influence of the static voltage error is excluded using a current program circuit, the common impedance of the power source lines 104 is large. Thus, unevenness in the dynamic current supply and the brightness unevenness is caused by the dynamic voltage variation, and deterioration in the display quality results. In order to solve this problem, both ends of the power source line 104 may be connected to power source terminals. For example, see Japanese Unexamined Patent Application Publication No. 2002-108252.